1. Field of the Invention
The present invention relates generally to ladder scaffolds, and particularly to ladder scaffolds suspended from rods inserted through hollow ladder rungs.
2. Description of Related Art
Ladders are well known for use in building construction and repair. Ladders do have certain deficiencies. Ladders provide only a very limited working space. If a ladder is leaning against a wall, any worker standing on the ladder has the ladder as a barrier between himself and the wall. He can reach the wall for only a short distance on either side of the ladder.
Scaffolds provide a platform having much greater working space, but have problems of their own. Adjusting the height of the scaffold is difficult. Climbing up and down the scaffold can be troublesome. Scaffolding is heavy and difficult to move around for jobs at various locations around a building. Scaffolding is also bulky and awkward to transport between jobs.
Pump jacks involve a pair of poles, each long enough to reach to the roof line of a building. A typical pole length would be 40 feet. The top of each pole is attached to the roof line, such as by nailing. A jack on each pole pumps up and down as desired. A platform is supported between the jacks, and its height is adjusted by pumping the jacks. Pump jacks are time consuming to set up. Pump jacks work relatively well for tasks such as putting up siding, where a worker is moving continuously in one direction. Pump jacks do not work well for tasks where a worker is working at just a few different heights. Pump jacks also are not suited for working at about the same height in various locations around a building. The pump jacks must be disassembled and set up again in each new location around the building. Pump jacks are expensive, and also bulky and awkward to transport.
Typical prior art ladder scaffolds attach to the side rails of a pair of ladders and are supported on the outside of the ladders. The ladders are still a barrier between a worker and the wall the ladders lean against. The scaffold also obstructs the ladders, so that the worker cannot easily go up and down past the scaffold. The worker is positioned at some distance from the wall, so that access to the wall itself is still relatively limited. Prior art ladder scaffolds are generally best for working above the roof line of a building, such as for putting on the first few rows of shingles on a roof. Prior art ladder scaffolds are generally complex and have a large number of small parts. The result is that essential parts are easily lost. Assembly and disassembly are time-consuming.
U.S. Pat. No. 3,266,593 by Okie et al. discloses a ladder scaffold made up of three ladder sections, and three ladder brackets connecting the ladder sections. The ladder brackets disclosed by Okie are quite complex. The ladder brackets include a pair of mirror-image bracket sections, each having a plate and two sleeve-like members to hold the side rails of the ladder. The mirror-image bracket sections of each ladder bracket are connected by hinges and a pair of turnbuckles. Each of the bracket sections may be secured to a ladder section by a pin. FIGS. 1 and 2 of Okie show six pins securing the three brackets. The pins may be threaded at each end, and may be inserted through hollow rungs in the ladder sections.
U.S. Pat. No. 3,491,852 by Leist discloses a ladder scaffold having a platform and braces. The platform is supported by hooks fitting into fastening slots in the ladders. The platform braces may have a plurality of regularly spaced holes for adjusting the length.
U.S. Pat. No. 4,941,547 by Livick discloses a ladder scaffold for use against a wall. The platform is supported by a pair of ladder jacks clamped by a U-bolt to the rungs of the ladder. Each ladder jack is a single triangular frame. Each ladder also has an antiflexing brace. The ladder scaffold includes a safety bar attached to the ends of the ladder jacks.
None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.